The proposed work is designed to characterize further the factors that are involved in the development of IgE-induced systemic anaphylactic shock in the rabbit. Studies will include the suceptibility of IgE-induced anaphylaxis as a function of age at the time of systemic challenge. These studies will be performed to determine whether there may be a developmental factor associated with the pharmacologic reactivity to various biogenic substances and whether such reactivity may be phenotypically altered. Cardiovascular pulmonary studies will be performed to further dilineate the physiologic changes accompanying the development of the shock syndrome. In the past we have demonstrated a dramatic effect upon the pulmonary circulation and the future studies will be designed to extend this work to determine whether changes in cardiac output occur and also to ascertain whether there might be a bronchopulmonary component in this syndrome. Lastly our most recent evidence indicates that specific IgE-antibody is capable of inducing profound blood coagulation alterations in vivo. The proposed work will be designed to further elucidate the mechanisms whereby IgE-antibody can lead to the activation of intrinsic coagulation and induce certain platelet changes. In addition, studies will be performed to determine whether such coagulation alterations are associated with the development of systemic hypotension in the IgE-induced systemic anaphylactic syndrome.